Power supply control circuit, power supply device and electronic apparatus

ABSTRACT

The present invention provides a power control circuit and a power device using the power control circuit, wherein quasi resonance is performed by the power control circuit using a coil, current flowing in the coil is monitored by a simple configuration, and a zero cross point or a bottom in resonance is detected. The present invention provides a power control circuit and a power device using the power control circuit. The power control circuit includes a detection circuit connected to a drain of MOSFET, the MOSFET serially connected between an inductor connected to an alternating-current wire and a current sensing resistor connected to ground potential; and a quasi resonance control circuit connected to the detection circuit and the MOSFET for performing quasi resonance control to inductor-current at a zero cross point or a bottom point in a time sequence of discharging while conducting the inductor-current of the inductor.

PRIORITY CLAIM AND CROSS-REFERENCE

The present invention claims priority under 35 U.S.C. § 119 to JapaneseApplication No. 2013-241521 filed Nov. 22, 2013, the entire content ofwhich is incorporated herein by reference.

BACKGROUND

The present invention relates to a power control circuit, a power deviceand electronic equipment, and more particularly, to a power controlcircuit, a power device and electronic equipment using coils to performquasi resonance.

Switch power devices performing quasi resonance (QR) are provided in theindustry (referring to patent literatures 1 to 5, for example.)

For example, in a circuit configuration performing quasi resonance,current flowing in a primary side coil of a DC/DC (direct current/directcurrent) converter has to be monitored, and thus a zero cross point in atime sequence of coil discharging or a bottom of resonance is detected.

BACKGROUND TECHNICAL LITERATURE Patent Literatures

-   [Patent literature 1] Japanese patent publication 2010-45939-   [Patent literature 2] Japanese patent publication 2007-110878-   [Patent literature 3] Japanese patent publication 2007-104759-   [Patent literature 4] Japanese patent publication 2009-527215-   [Patent literature 5] WO2011/122314

BRIEF SUMMARY OF THE INVENTION Problem to be Solved in the PresentInvention

It is an object of the present invention to provide a power controlcircuit, a power device and an electronic equipment using the powercircuit, wherein a coil is used to perform quasi resonance in the powercontrol circuit, current flowing in the coil is monitored with a simpleconfiguration, and a bottom detection at a zero cross point or quasiresonance is performed.

Technical Solution

In accordance with an aspect of the present invention, a power controlcircuit is provided. The power control circuit includes: a high passfilter connected to a drain of a metal-oxide-semiconductor field effecttransistor (MOSFET), which is serially connected between an inductorconnected to an alternating-current wire and a current sensing resistorconnected to a ground potential; and a quasi-resonant control circuitconnected to the high pass filter and the MOSFET, wherein when aninductor-current of the inductor is conducted in a discharging timesequence, the quasi resonance control circuit performs quasi resonancecontrol upon the inductor-current of the inductor at a zero crossingpoint or a bottom point in the discharging time sequence based on anoutput of the high pass filter.

In accordance with another aspect of the present invention, a powerdevice is provided. The power device includes an inductor connected toan alternating-current wire; a current sensing resistor connected to aground potential; a MOSFET connected between the inductor and thecurrent sensing resistor in series; a high pass filter connected to adrain of the MOSFET; and a quasi-resonant control circuit connected tothe high pass filter and the MOSFET, wherein when an inductor-current ofthe inductor is conducted in a discharging time sequence, the quasiresonance control circuit performs quasi resonance control upon theinductor-current of the inductor at a zero crossing point or a bottompoint in the discharging time sequence based on an output of the highpass filter.

In accordance with another aspect, electronic equipment having the abovepower device is provided.

Effects of the Present Invention

In accordance with the present invention, a power control circuit, apower device and an electronic equipment using the power control circuitare provided, wherein a coil is used to perform quasi resonance in thepower control circuit, and current flowing in the coil is monitored witha simple configuration so as to perform a bottom detection at a zerocross point or resonance.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a schematic circuit configuration of a power devicein accordance with a comparative example.

FIG. 2 illustrates a detailed circuit configuration of a power device inaccordance with a comparative example.

FIG. 3 illustrates a schematic circuit configuration of a power devicein accordance with some embodiments of the present invention.

FIG. 4 illustrates a detailed circuit configuration of a power device inaccordance with some embodiments of the present invention.

FIG. 5(a) illustrates a circuit configuration of an auxiliary winding ofa transformer and an inductor of a power device in accordance with acomparative example, and FIG. 5(b) shows a circuit configuration of aninductor of a power device in accordance with some embodiment of thepresent invention.

FIG. 6 illustrates the operations of performing pulse-width modulation(PWM) frequency fixing control without using QR frequency control, inwhich (a) shows an exemplary waveform of a gate voltage V_(G), (b) showsan exemplary waveform of a current sensing voltage V_(CS), (c) shows anexemplary waveform of inductor-current I_(L), (d) shows an exemplarywaveform of a drain voltage V_(D), and (e) shows an exemplary waveformof a regulator terminal voltage V_(ZT).

FIG. 7 illustrates operations of a power device using QR frequencycontrol in accordance with a comparative example, in which (a) shows anexemplary waveform of a gate voltage V_(G), (b) shows an exemplarywaveform of a current sensing voltage V_(CS), (c) shows an exemplarywaveform of inductor-current I_(L), (d) shows an exemplary waveform of adrain voltage V_(D), and (e) shows an exemplary waveform of a regulatorterminal voltage V_(ZT).

FIG. 8 illustrates operations of a power device using QR frequencycontrol in accordance with some embodiments of the present invention, inwhich (a) shows an exemplary waveform of a gate voltage V_(G), (b) showsan exemplary waveform of a current sensing voltage V_(CS), (c) shows anexemplary waveform of inductor-current I_(L), (d) shows an exemplarywaveform of a drain voltage V_(D), and (e) shows an exemplary waveformof a high pass filer (HPF) terminal voltage V_(HP).

FIG. 9 illustrates operations of a power device using QR frequencycontrol in accordance with some embodiments of the present invention, inwhich (a) shows an exemplary waveform of inductor-current I_(L), (b)shows an exemplary waveform of a gate voltage V_(G), (c) shows anexemplary waveform of a drain voltage V_(D), (d) shows an exemplarywaveform of an HPF terminal voltage V_(HP) (e) shows an exemplarywaveform of a setting voltage V_(SET), and (f) shows an exemplarywaveform of a reset voltage V_(RESET).

FIG. 10 illustrates detailed operations of a power device using QRfrequency control in accordance with some embodiments of the presentinvention, in which (a) shows an exemplary waveform of an HPF terminalvoltage V_(HP), and (b) shows various waveforms of an HPF terminalvoltage V_(HP).

FIG. 11 illustrates a circuit block diagram showing experimentaloperations of a power device in accordance with some embodiments of thepresent invention.

FIG. 12 illustrates results of experimental operations of a power devicein accordance with some embodiments of the present invention, in whichan exemplary waveform of a drain voltage V_(D), an exemplary waveform ofan HPF terminal voltage V_(HP) and an exemplary waveform ofinductor-current I_(L) are illustrated.

FIG. 13 illustrates results of experimental operations of a power devicein accordance with some embodiments of the present invention, in whichan exemplary waveform of a drain voltage V_(D), an exemplary waveform ofa regulator terminal voltage V_(ZT) and an exemplary waveform ofinductor-current I_(L) are illustrated.

FIG. 14 illustrates a schematic circuit configuration showing a powerdevice in accordance with some embodiments of the present invention, inwhich an illumination device, a light emitting diode, is illustrated.

FIG. 15 illustrates a schematic circuit configuration showing a powerdevice in accordance with some embodiments of the present invention, inwhich a flyback LED illumination device is illustrated.

FIG. 16 illustrates a schematic circuit configuration showing a powerdevice in accordance with some embodiments of the present invention, inwhich a QR type DC/DC converter is illustrated.

FIG. 17 illustrates a schematic circuit configuration showing a powerdevice in accordance with some embodiments of the present invention, inwhich an AC/DC converter is illustrated.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Then, embodiments of the present invention are illustrated in light ofdrawings. In the following descriptions and drawings, similar oridentical reference numerals are referred to similar or identicalelements. However, it should be noted that the drawing s are schematicviews, and the size and thickness of each element may not be drawn inscale. Therefore, the specific thickness or size should be determinedaccording to the following descriptions. Further, the size relationshipor different ratio is certainly included among the drawings.

Furthermore, the technical concept of the present invention is specifiedas a device or a method, which is illustrated in the followingembodiments. The material, shape, structure, arrangement and etc. ofeach component of the present invention are not limited to the followingembodiments. Variations may be applied to the following embodimentswithout departing the scope or spirit of claims of the presentinvention.

Comparative Example

FIG. 1 illustrates a circuit configuration of a power device 4Aaccording to a comparative example. Further, the detailed circuitconfiguration is shown in FIG. 2. The power device 4A of the comparativeexample is corresponding to a buck LED illumination device.

As shown in FIG. 1, the power device 4A of the comparative exampleincludes: a diode bridge (DB) 14 connected to an AC input; anelectrolytic capacitor CE connected to the diode bridge (DB) 14; ainductor L_(P) connected to an AC wire side via a load (LED); a currentsensing resistor R_(S) connected to ground potential; a plurality ofMOSFET Qs connected between the inductor L_(P) and the current sensingresistor R_(S) in series; and a power control circuit 2A coupled to theinductor L_(P), the MOSFET Qs and the current sensing resistor R_(S) forperforming QR control to inductor-current I_(L) flowing through theinductor L_(P).

The power control circuit 2A includes: a detection circuit 32A for theinductor-current I_(L) flowing through the inductor L_(P); and a QRcontrol circuit 30 connected to the detection circuit 32A, the MOSFET Qsand the current sensing resistor R_(S) for performing QR control uponthe inductor-current I_(L) at a zero cross point or bottom point in thedischarging time sequence of discharging the inductor L_(P) based on anoutput of the detection circuit 32A.

Herein, the detection circuit 32A includes: an auxiliary wiring inductorL_(a) electromagnetically coupled to the inductor L_(P); and a firstresistor R1 and a second resistor R2 connected between the auxiliarywiring inductor L_(a) and ground potential in series.

More specifically, as shown in FIG. 2, the power device 4A of thecomparative example includes: a filter circuit 12 connected to the ACinput; a diode bridge (DB) 14 connected to the filter bridge 12; an LCcircuit (L1-C1) connected to the diode bridge (DB) 14 for smoothing arectified waveform; an inductor L_(P) connected to an AC input a load(LED); a current sensing resistor R_(S) connected to ground potential;MOSFET Qs connected between the inductor L_(P) and the current sensingresistor R_(S) in series; and a power control circuit 2A coupled to theinductor L_(P), the MOSFET Qs, the current sensing resistor R_(S) forperforming QR control to inductor-current I_(L) flowing through theinductor L_(P).

Moreover, as shown in FIG. 2, the power device 4A of the comparativeexample includes: a regeneration capacitor C_(C) connected to aninductor L_(P) in series and connected to a load (LED) in parallel; anda regeneration diode (buffer diode) D_(C) connected to the regenerationcapacitor C_(C) and the inductor L_(P) in parallel, which are connectedin series. Further, a capacitor C2 is equivalently connected betweensources and drains of the MOSFET Qs.

In comparison with a drain voltage V_(D) of the MOSFET Qs connected tothe inductor L_(P), a regulator terminal voltage V_(ZT) at theconnection point connecting the first resistor R1 and the secondresistor R2 of a regulator terminal ZT connected to the QR controlcircuit 30 is reduced to 1/100, for example. Further, as shown in FIG.2, a Zener diode ZD is connected to the regulator terminal ZT.

As shown in FIG. 2, the QR control circuit 30 applied to the powerdevice 4A of the comparative example includes: a current detectioncomparator 34 connected to the regulator terminal ZT; an error amplifier40 connected to a current sensing terminal CS and performing acomparison with a reference voltage V_(ref); an RS trigger 36 connectedto an output of the current detection comparator 34 and an output of theerror amplifier 40 and outputting a control signal of the MOSFET Qs; anda buffer 38 connected to an output Q of the RS trigger 36 and drivingthe MOSFET Qs.

Herein, the MOSFET Qs are controlled to be conductive while the RStrigger 36 performs a setting action, and the MOSFET Qs are controlledto be non-conductive while the RS trigger 36 performs a resettingaction.

In the power control circuit 2A applied in the power device 4A of thecomparative example, an auxiliary wire of a transformer is wound to forman auxiliary wiring inductor La. In other words, the zero cross point ora bottom point is monitored by the detection circuit 32A using theauxiliary winding.

In the comparative example, the power device 4A for the LED illuminationneeds the auxiliary winding of the transformer, and thus the totalweight and volume of the transformer are increased.

Embodiments

FIG. 3 illustrates a schematic circuit configuration of a power device 4according to an embodiment of the present invention. Further, thedetailed circuit configuration is shown in FIG. 4. The power device 4 ofthe embodiment is corresponding to a buck LED illumination device.

As shown in FIG. 3, the power device 4 includes: a diode bridge (DB) 14connected to an AC input; an electrolytic capacitor CE connected to thediode bridge (DB) 14; an inductor L_(P) connected to an AC wire side viaa load (LED); a current sensing resistor R_(S) connected to groundpotential; MOSFET Qs connected between the inductor L_(P) and thecurrent sensing resistor R_(S) in series; and a power control circuit 2coupled to the inductor L_(P), the MOSFET Qs and the current sensingresistor R_(S) for performing QR control to inductor-current I_(L)flowing through the inductor L_(P).

The power control circuit 2 includes: a detection circuit 32 fordetecting inductor-current I_(L) flowing through the inductor L_(P); aQR control circuit 30 connected to the detection circuit 32, the MOSFETQs and the current sensing resistor R_(S), wherein when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, the quasi resonance control circuit 30performs quasi resonance control upon the inductor-current I_(L) of theinductor L_(P) at a zero crossing point or a bottom point in thedischarging time sequence based on an output of the detection circuit32.

Herein, the detection circuit 32 may include a high pass filer (HPF)connected to a drain of the MOSFET Qs connected to the inductor L_(P).

As shown in FIG. 3 and FIG. 4, the HPF includes: a capacitor C_(F)connected to a drain of MOSFET Qs; and a first resistor R_(f1) and asecond resistor R_(f2) connected between the capacitor C_(F) and groundpotential in series, and a regulator terminal ZT of a QR control circuit30 is connected to a connection point connecting the first resistorR_(f1) and the second resistor R_(f2).

The zero cross point is monitored by the power control circuit 2 usingthe HPF, wherein the power control circuit 2 is applied to the powerdevice 4 of the embodiment. The decreasing of the drain voltage V_(D)may be detected by an AC component of the HPF. In other words, adecreasing point of a waveform of the drain voltage V_(D) may bedetected by the HPF.

The QR control circuit 30 is used for connecting an output OUT to a gateof MOSFET Qs, detecting current conducted in the detection circuit 32,and, when the inductor-current I_(L) of the inductor L_(P) is conductedin a discharging time sequence, controlling the MOSFET Qs to conduct ata zero cross point or a bottom point in the discharging time sequencebased on an output of the detection circuit 32.

Further, the QR control circuit 30 may be used for detecting currentconducted in the current sensing resistor R_(S), and controlling theMOSFET Qs to be non-conductive at a specific reset time point.

More specifically, as shown in FIG. 4, a power device 4 of theembodiment includes: a filter circuit 12 connected to an AC (AlternativeCurrent) input; a diode bridge (DB) 14 connected to the filter circuit12; an LC circuit (L1-C1) connected to the diode bridge (DB) 14 forsmoothing a rectified waveform; an inductor L_(P) connected to the ACinput side via a load (LED); a current sensing resistor R_(S) connectedto ground potential; MOSFET Qs connected between the inductor L_(P) andthe current sensing resistor R_(S) in series; and a power controlcircuit 2 coupled to the inductor L_(P), the MOSFET Qs and the currentsensing resistor R_(S) for performing QR control to inductor-currentI_(L) flowing in the inductor L_(P).

Furthermore, as shown in FIG. 4, the power device 4 of the embodimentincludes: a regeneration capacitor C_(C) connected to the inductor L_(P)in series and connected to a load (LED) in parallel; and a regenerationdiode (buffer diode) D_(C) connected to the regeneration capacitor C_(C)and the inductor L_(P) in parallel, which are connected in series.Further, a capacitor C2 is equivalently connected between a drain and asource of the MOSFET Qs.

In the detection circuit 32, a direct current component of an HPFterminal voltage V_(HP) at the connection point connecting the capacitorC_(F) and the first resistor RD is blocked by the capacitor C_(F), and apotential difference between a high level and a low level is the samelevel as a potential difference of a drain voltage V_(D) of the MOSFETQs. On the other hand, in comparison with a drain voltage V_(D) of theMOSFET Qs, a regulator terminal voltage V_(ZT) at a connection pointconnecting the first resistor R_(f1) and the second resistor R_(f2) ofthe regulator terminal ZT connected to the QR control circuit 30 isreduced to less than 1/100, for example, and becomes as a differentialwaveform with a peak shape. Further, as shown in FIG. 4, a Zener diodeZD is connected to the regulator terminal ZT.

As shown in FIG. 4, the QR control circuit 30 of the power device 4applied in the embodiment includes: a current detection comparator 34connected to a regulator terminal ZT; an error amplifier 40 connected toa current sensing terminal CS and performing a comparison with areference voltage V_(ref); an RS trigger 36 connected to an output ofthe current detection comparator 34 and an output of the error amplifier40, and outputting a control signal of the MOSFET Qs; and a buffer 38connected to an output Q of the RS trigger 36 for driving MOSFET Qs.

Herein, the MOSFET Qs are controlled to be conductive at a time point ofsetting actions of the RS trigger 36, and the MOSFET Qs are controlledto be non-conductive at a time point of resetting actions of the RStrigger 36.

In the power device 4 of the embodiment, while the MOSFET Qs areconducted, as shown in FIG. 4, inductor-current I_(L) of the load (LED),the inductor L_(P) and the MOSFET Qs and discharge current I_(dis1) ofthe capacitor C2 are conducted from an AC wire side. On the other hand,while the MOSFET Qs are off, regeneration current I_(LC) of theregeneration capacitor C_(C), the inductor L_(P) and the regenerationdiode (buffer diode) D_(C) and discharge current I_(dis2) of thecapacitor C2 are conducted to flow.

FIG. 5(a) is a circuit configuration showing an auxiliary winding and aninductor of a transformer of a power device in a comparative example.Herein, an inductor L_(P) has a value of about 1 mH, for example, and anauxiliary winding inductor L_(a) has a value of about 100 μH, forexample. FIG. 5(b) illustrates a circuit configuration of an inductor ofa power device according to an embodiment. Herein, an inductor L_(P) hasa value of about 1 mH, for example, and having the same level as thevalue of the inductor L_(P) shown in FIG. 5(a).

The detection circuit 32 of the power control circuit 2 applied in thepower device 4 of the embodiment may be formed by a HPF with simplecircuitry. Further, there is no need to use an auxiliary winding of atransformer, so as to reduce the total weight and volume of thetransformer.

The power device 4 of the embodiment forms a buck LED illuminationdevice using the inductor L_(P) rather than using an auxiliary windinginductor, so as to achieve applications with low cost and highefficiency.

Comparative Example: PWM Fixed Frequency Control

FIG. 6 illustrates the operation of PWM fixed frequency control withoutusing QR frequency control, wherein FIG. 6(a) shows an exemplarywaveform of a gate voltage V_(G), FIG. 6(b) shows an exemplary waveformof a current sensing voltage V_(CS), FIG. 6(c) shows an exemplarywaveform of inductor-current I_(L), FIG. 6(d) shows an exemplarywaveform of a drain voltage V_(D), and FIG. 6(e) shows an exemplarywaveform of a regulator terminal voltage V_(ZT).

In the operations of the PWM fixed frequency control, a PWM signal witha fixed frequency is input to a setting terminal S of the RS trigger 36shown in FIG. 2. As shown in FIG. 6(a), an exemplary waveform of a gatevoltage V_(G) has a fixed period T_(f)(FIXED). Along with the fixedperiod T_(f)(FIXED), the fixed frequency of the PWM is in a range fromabout 100 kHz to about 300 kHz.

First, at time t1, as shown in FIG. 6(a), when the waveform of the gatevoltage V_(G) is in the status of being conducted (ON), the MOSFET Qsare conductive, the waveform of the current sensing voltage V_(CS) isincreased as shown in FIG. 6(b), and the exemplary waveform of theinductor-current I_(L) is also increased as shown in FIG. 6(c). On theother hand, the waveform of the drain voltage V_(D) is kept at zeropotential shown in FIG. 6(d), and also the waveform of the regulatorterminal voltage V_(ZT) is kept at zero potential as shown in FIG. 6(e).

Next, at time t2, the PWM signal is off, as shown in FIG. 6(a), and whenthe waveform of the gate voltage V_(G) is in the status of beingnon-conducted (OFF), in comparison with the reference voltage V_(ref),the current sensing voltage V_(CS) is dramatically reduced as shown inFIG. 6(b). On the other hand, as shown in FIG. 6(c), during time t2 totime t21, the waveform of the inductor-current I_(L) is graduallyreduced from the current value I_(L1) at time t2. Further, the waveformof the drain voltage V_(D) is dramatically increased to a voltage V_(DH)as shown in FIG. 6(d), and also the waveform of the regulator terminalvoltage V_(ZT) is dramatically increased to a voltage V_(ZTH) as shownin FIG. 6(e). Herein, a pulse height ΔV_(ZTH) of the regulator terminalvoltage V_(ZT) is about 1/100 of a pulse height ΔV_(DH) of the drainvoltage V_(D), for example. This is because the resistance of the firstresistor R1 and the second resistor R2 serially connected between theauxiliary winding inductor L_(a) and ground potential shown in FIG. 2 isdivided and the voltage value is reduced.

Next, at time t21, when the exemplary waveform of the inductor-currentI_(L) is zero, as shown in FIG. 6(d), the waveform of the drain voltageV_(D) becomes a vibration-reduced waveform having zero cross points B1,B2, B3, B4, . . . , B9 and taking a zero potential level as a center,and noise BN is produced. Meanwhile, as shown in FIG. 6(e), the waveformof the regulator terminal voltage V_(ZT) becomes a vibration-reducedwaveform taking a zero potential level as a center. Thevibration-reduced waveform is determined by the turned-off operation ofthe MOSFET Qs and a parasitic RLC circuit component connected to thedrain of the MOSFET Qs.

Next, after fixed time determined by the fixed period T_(f)(FIXED), attime t3, the waveform of the gate voltage V_(G) is again in the statusof being conducted (ON), and then the same operations between time t1and time t3 are repeated.

In the operations of the PWM with fixed frequency control, the frequencyof the PWM is fixed, and the noise waveforms are generated as shown inFIG. 6(d) and FIG. 6(e).

Comparative Example: QR Frequency Control

FIG. 7 illustrates operations of a power device 4A (FIG. 1 and FIG. 2)using QR frequency control according to a comparative example, whereinFIG. 7(a) shows an exemplary waveform of a gate voltage V_(G), FIG. 7(b)shows an exemplary waveform of a current sensing voltage V_(CS), FIG.7(c) shows an exemplary waveform of inductor-current I_(L), FIG. 7(d)shows an exemplary waveform of a drain voltage V_(D), and FIG. 7(e)shows an exemplary waveform of a regulator terminal voltage V_(ZT).

First, at time t1, as shown in FIG. 7(a), when the waveform of the gatevoltage V_(G) is in the status of being conducted (ON), the MOSFET Qsare conductive, the waveform of the current sensing voltage V_(CS) isincreased as shown in FIG. 7(b), and the exemplary waveform of theinductor-current I_(L) is also increased as shown in FIG. 7(c). As shownin FIG. 7(d), the waveform of the drain voltage V_(D) is changed fromthe fixed voltage V_(DH) to zero potential. On the other hand, as shownin FIG. 7(e), the waveform of the regulator terminal voltage V_(ZT) iscorresponding to potential of a connection point of serially connectedresistors (R_(f1)+R_(f2)) in the detection circuit 32, so as to become areduced pulse waveform depending upon a pulse waveform of the waveformof the drain voltage V_(D) during time 0 to time t1. A pulse heightΔV_(ZTH) of the regulator terminal voltage V_(ZT) is about 1/100 of apulse height ΔV_(DH) of the drain voltage V_(D), for example. This isbecause the resistance of the first resistor R1 and the second resistorR2 serially connected between the auxiliary winding inductor L_(a) andground potential shown in FIG. 2 is divided and the voltage value isreduced. At time t1, a bottom BT of the waveform of the drain voltageV_(D) is detected.

During time t1 to time t2, the drain voltage V_(D) and the regulatorterminal voltage V_(ZT) are kept at zero potential.

Next, at time t2, as shown in FIG. 7(a), when a reset signal is input tothe resetting terminal R of the RS trigger 36 so as to cause thewaveform of the gate voltage V_(G) in the status of being non-conducted(OFF), in comparison with the reference voltage V_(ref), the currentsensing voltage V_(CS) is dramatically reduced as shown in FIG. 7(b). Onthe other hand, as shown in FIG. 7(c), during time t2 to time t3, thewaveform of the inductor-current I_(L) is gradually reduced. On theother hand, as shown in FIG. 7(d), the waveform of the drain voltageV_(D) is dramatically increased to a voltage V_(DH), and then kept at asubstantially fixed voltage V_(DH). Meanwhile, as shown in FIG. 7(e),the waveform of the regulator terminal voltage V_(ZT) is dramaticallyincreased at time t2 to a voltage V_(ZTH), and then kept at asubstantially fixed voltage V_(ZTH).

Meanwhile, as shown in FIG. 7(c), during time t2 to time t3, thewaveform of the inductor-current I_(L) is reduced from the current valueI_(L1) at time t2 to near zero level.

As shown in FIG. 7(d), near time t3, the waveform of the drain voltageV_(D) is dramatically reduced from a substantially fixed voltage V_(DH)to near zero level. Similarly, as shown in FIG. 7(e), the waveform ofthe regulator terminal voltage V_(ZT) is dramatically reduced from asubstantially fixed voltage V_(ZTH) to near zero level. Herein, time t3is corresponding to the time point of the bottom detection. Whiledetecting the bottom BT at time t1 and time t3, the waveform of the gatevoltage V_(G) is in a status of being conducted (ON). Then, the sameoperations between time t1 and time t3 are repeated.

In the power device (FIG. 1 and FIG. 2) using QR frequency controlaccording to a comparative example, an auxiliary winding inductor L_(a)is used, so as to increase the total weight and volume of thetransformer.

Embodiment: QR Frequency Control

FIG. 8 illustrates operations of a power device (FIG. 3 and FIG. 4)using QR frequency control according some embodiments of the presentinvention, wherein FIG. 8(a) shows an exemplary waveform of a gatevoltage V_(G), FIG. 8(b) shows an exemplary waveform of a currentsensing voltage V_(CS), FIG. 8(c) shows an exemplary waveform ofinductor-current I_(L), FIG. 8(d) shows an exemplary waveform of a drainvoltage V_(D), and FIG. 8(e) shows an exemplary waveform of an HPFterminal voltage V_(HP).

First, at time t1, as shown in FIG. 8(a), when the waveform of the gatevoltage V_(G) is in the status of being conducted (ON), the MOSFET Qsare conductive, the waveform of the current sensing voltage V_(CS) isincreased as shown in FIG. 8(b), and the exemplary waveform of theinductor-current I_(L) is also increased as shown in FIG. 8(c). As shownin FIG. 8(d), the waveform of the drain voltage V_(D) is changed fromthe fixed voltage V_(DH) to zero potential. On the other hand, as shownin FIG. 8(e), the waveform of the HPF terminal voltage V_(HP) iscorresponding to the potential at two ends of the serially connectedresistors (R_(f1)+R_(f2)) in the HPF, so as to become a differentialwaveform depending on a transient response of the waveform of the drainvoltage V_(D). The bottom BT is detected at time t1. After the detectionof the bottom BT, the drain voltage V_(D) and the HPF terminal voltageV_(HP) are kept at zero potential till time t2.

Next, at time t2, when a reset signal is input to a resetting terminal Rof the RS trigger 36 and thus the gate voltage V_(G) is off, thewaveform of the gate voltage V_(G) is dramatically reduced as shown inFIG. 8(a), and also the current sensing voltage V_(CS) in comparisonwith the reference voltage V_(ref) is dramatically reduced as shown inFIG. 8(b). On the other hand, as shown in FIG. 8(c), the waveform of theinductor-current I_(L) is gradually reduced from the current valueI_(L1) at time t2 between time t2 and time t3. On the other hand, asshown in FIG. 8(d), the waveform of the drain voltage V_(D) at time t2is dramatically increased to a voltage V_(DH), and then kept at asubstantially fixed voltage V_(DH). Furthermore, as shown in FIG. 8(e),the waveform of the HPF terminal voltage V_(HP) becomes a differentialwaveform depending on a transient response of the waveform of the drainvoltage V_(D). After the transient response, the drain voltage V_(D) iskept at a substantially fixed voltage V_(DH) and the HPF terminalvoltage V_(HP) is kept at zero potential till time t3.

Next, near time t3, the waveform of the drain voltage V_(D) isdramatically reduced from a substantially fixed voltage V_(DH) to nearzero level as shown in FIG. 8(d). On the other hand, as shown in FIG.8(e), the waveform of the HPF terminal voltage V_(HP) becomes adifferential waveform depending on a transient response of the waveformof the drain voltage V_(D). The bottom BT is detected at time t3. Whiledetecting the bottoms BT at time t1 and time t3, the gate voltage V_(G)is in the status of being conducted (ON).

The zero cross point is monitored by the power device 4 using the HPFaccording to some embodiments of the present invention. The bottom BTmay be detected by using the AC component of the HPF at the time pointat which the drain voltage V_(D) is decreased. In other words, the HPFmay be used to detect the decreasing point of the waveform of the drainvoltage V_(D).

Then, the same operations between time t1 and time t3 are repeated.

Further, FIG. 9 illustrates detailed operations of a power device usingQR frequency control according to some embodiments of the presentinvention, wherein FIG. 9(a) shows an exemplary waveform ofinductor-current I_(L), FIG. 9(b) shows an exemplary waveform of a gatevoltage V_(G), FIG. 9(c) shows an exemplary waveform of a drain voltageV_(D), FIG. 9(d) shows an exemplary waveform of an HPF terminal voltageV_(HP), FIG. 9(e) shows an exemplary waveform of a set voltage V_(SET),and FIG. 9(f) shows an exemplary waveform of a reset voltage V_(RESET).FIG. 9(a) is corresponding to FIG. 8(c), FIG. 9(b) is corresponding toFIG. 8(a), FIG. 9(c) is corresponding to FIG. 8(d), and FIG. 9(d) iscorresponding to FIG. 8(e). Similarly, a bottom is detected at time t1and time t3.

As shown in FIG. 9(e), an exemplary waveform of a set voltage V_(SET)which is input to the setting terminal S of the RS trigger 36 (FIG. 4)is implemented at time t1 and time t3. As shown in FIG. 9(f), anexemplary waveform of a reset voltage V_(RESET) which is input to theresetting terminal R of the RS trigger 36 (FIG. 4) is implemented attime t2 and time t4. In other words, in the power device 4 (FIG. 3 andFIG. 4) using QR frequency control according to embodiments of thepresent invention, the conduction control of MOSFET Qs is implemented atthe time point at which the RS trigger 36 performs setting actions, andthe non-conduction control of MOSFET Qs is implemented at the time pointat which the RS trigger 36 performs resetting actions. Other actions aresimilar to those in FIG. 8, and thus the associated descriptions areomitted.

In the power device 4 (FIG. 3 and FIG. 4) using QR frequency controlaccording to embodiments of the present invention, in comparison withthe comparative example using an auxiliary winding of a transformer,there is no need to use an auxiliary winding of a transformer, so as toreduce the total weight and volume of a transformer.

(Exemplary waveform of an HPF terminal voltage V_(HP))

Further, FIG. 10 illustrates detailed operations of a power device usingQR frequency control according to embodiments of the present invention,wherein FIG. 10(a) shows an exemplary waveform of an HPF terminalvoltage V_(HP), and FIG. 10(b) shows various exemplary waveforms of theHPF terminal voltage V_(HP). The exemplary waveform in FIG. 10(a) iscorresponding to that in FIG. 8(e) or FIG. 9(d). On the other hand, asshown in FIG. 10(b), the exemplary waveform of the HPF terminal voltageV_(HP) has various shapes according to a value of a time constant(R_(f1)+R_(f2))C_(F) determined by a capacitor C_(F), a first resistorR_(f1) and a second resistor R_(f2) of the HPF. In FIG. 10(b), thevalues of the time constant are increased and set according to H1, H2,H3 and H4 in sequence.

(Results of Experiments)

FIG. 11 is a circuit block diagram showing experimental operations of apower device 4 in accordance with some embodiments of the presentinvention. In FIG. 11, a diode bridge (DB) 14 is omitted forsimplification. An input voltage V_(in) is corresponding to a full waverectified waveform of the rectified AC input.

In FIG. 11, the circuit constants of the HPF are illustrated as follows.For example, the value of the capacitor C_(F) is about 100 pF, and thewithstand voltage of the capacitor C_(F) is about 1 kV. The value of thefirst resistor R_(f1) is about 1 MΩ, and the value of the secondresistor R_(f2) is about 10 1 kΩ, for example. Accordingly, the value ofthe time constant (R_(f1)+R_(f2))C_(F) is about 0.1 msec.

For example, the operation switching frequency of the power deviceaccording to embodiments of the present invention is in a range fromabout 20 kHz to about 200 kHz.

Further, FIG. 12 illustrates results of experimental operations of apower device 4 in accordance with some embodiments of the presentinvention, in which an exemplary waveform of a drain voltage V_(D), anexemplary waveform of an HPF terminal voltage V_(HP) and an exemplarywaveform of inductor-current I_(L) are illustrated. The action waveformsshown in FIG. 12 are corresponding to the exemplary waveforms of thedrain voltage V_(D) in FIG. 8(d) and FIG. 9(c), the exemplary waveformsof the HPF terminal voltage V_(HP) in FIG. 8(e) and FIG. 9(d), and theexemplary waveforms of the inductor-current I_(L) in FIG. 8(c) and FIG.9(a).

The vertical axis of the waveform of the drain voltage V_(D) is 100V/div, and the duty cycle is about 74.5%. Further, the operationswitching frequency of the drain voltage V_(D) is about 48.30 kHz.

In the detection circuit 32, the DC component of the waveform of thedrain voltage V_(D) is blocked by the capacitor C_(F) to form an outputwaveform of the HPF terminal voltage V_(HP). The vertical axis of thewaveform of the HPF terminal voltage V_(HP) iS 100 V/div.

The vertical axis of the waveform of the inductor-current IL is 500mA/div, and the horizontal axis is 5 μsec/div.

Further, FIG. 13 illustrates results of experimental operations of apower device 4 in accordance with some embodiments of the presentinvention, in which an exemplary waveform of a drain voltage V_(D), anexemplary waveform of a regulator terminal voltage V_(ZT) and anexemplary waveform of inductor-current I_(L) are illustrated. The actionwaveforms shown in FIG. 13 are corresponding to the exemplary waveformsof the drain voltage V_(D) in FIG. 8(d) and FIG. 9(c), the exemplarywaveform of the regulator terminal voltage V_(ZT) in FIG. 7(e) under thesame detection in the comparative example, and the exemplary waveformsof the inductor-current I_(L) in FIG. 8(c) and FIG. 9(a). The exemplarywaveform of the regulator terminal voltage V_(ZT) shown in FIG. 13 iscorresponding to the potential of the connection point connecting thefirst resistor R_(f1) and the second resistor R_(f2).

The vertical axis of the waveform of the drain voltage V_(D) is 100V/div, and the duty cycle is about 77.86%. Further, the operationswitching frequency of the drain voltage V_(D) is about 52.71 kHz.

The vertical axis of the waveform of the regulator terminal voltage is500 mV/div. The waveform of the regulator terminal voltage V_(ZT) isobtained by dividing the waveform of the HPF terminal voltage V_(HP) bythe divided resistance of the first resistor R_(f1) and the secondresistor R_(f2), and is input to the regulator terminal ZT of the QRcontrol circuit 30.

When the value, 0.1 V, is obtained from the detection of the regulatorterminal ZT, it starts to perform the switching operation. In otherwords, when the regulator terminal voltage V_(ZT) which is input to theregulator terminal ZT of the QR control circuit 30 is more than 0.1 V, acurrent detection comparator 34 (FIG. 4) is activated due to theactivation of the Zener diode, and a waveform of a set voltage V_(SET)(FIG. 9(e)) is input to the setting terminal S of the RS trigger 36(FIG. 4).

It is similar to FIG. 12 that the vertical axis of the waveform of theinductor-current I_(L) is 500 mA/div, and the horizontal axis is 5μsec/div.

(Boost LED Illumination Device)

The power control circuit 2 of embodiments of the present invention maybe applied in various power devices. In addition to the buck LEDillumination device, the power control circuit 2 may be applied in aboost LED illumination device, a flyback LED illumination device andetc.

FIG. 14 illustrates a schematic circuit block diagram of the powerdevice 6 using the power control circuit 2 according to embodiments ofthe present invention, which is a boost LED illumination device. Theinput voltage V_(in) is corresponding to a full wave rectified waveformof the rectified input AC.

As shown in FIG. 14, the power device 6 according to embodiments of thepresent invention includes an inductor L_(P) connected to an AC wireside; a current sensing resistor R_(S) connected to ground potential;MOSFET Qs connected between the inductor L_(P) and the current sensingresistor R_(S) in series; and a power control circuit 2 coupled to theinductor L_(P), the MOSFET Qs and the current sensing resistor R_(S) forperforming QR control upon the current I_(L) flowing through theinductor L_(P).

The power control circuit 2 includes a detection circuit 32 fordetecting the inductor-current I_(L) flowing through the inductor L_(P);and a QR control circuit 30 connected to the detection circuit 32, theMOSFET Qs and the current sensing resistor R_(S), wherein when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, the QR control circuit 30 performs QR controlupon the inductor-current I_(L) of the inductor L_(P) at a zero crossingpoint or a bottom point in the discharging time sequence based on anoutput of the detection circuit 32.

Herein, the detection circuit 32 may include an HPF connected to a drainof the MOSFET Qs connected to the inductor L_(P).

As shown in FIG. 14, the HPF includes a capacitor C_(F) connected to adrain of the MOSFET Qs; and a first resistor R_(f1) and a secondresistor R_(f2) connected between the capacitor C_(F) and the groundpotential in series, and a regulator terminal ZT of the QR controlcircuit 30 is connected to a connection point connecting the firstresistor R_(f1) and the second resistor R_(f2).

An output OUT is connected to a gate of the MOSFET Qs by the QR controlcircuit 30 for detecting current conducted in the HPF, and, when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, controlling the MOSFET Qs to conduct at azero cross point or a bottom point in the discharging time sequencebased on an output of the detection circuit 32.

Further, the QR control circuit 30 may detect current conducted in thecurrent sensing resistor R_(S), and control the MOSFET Qs to benon-conductive at a specific reset time point.

As shown in FIG. 14, in the power device 6 according to embodiments ofthe present invention, an inductor L_(P) is connected to a regenerationcapacitor C_(B) and a regeneration diode (buffer diode) D_(B) inparallel, which are connected in series, and the regeneration capacitorC_(B) is connected to a load (LED) in parallel, so as to form a boostLED illumination device. Other configurations are similar to the powerdevice 4 according to embodiments of the present invention, and thus theassociated descriptions are omitted.

By using the power device 6 according to embodiments of the presentinvention, the boost LED illumination device includes an inductor L_(P)rather than using an auxiliary winding inductor, so as to reduce thetotal weight and volume of the transformer, lower cost and increaseefficiency.

(Flyback LED Illumination Device)

FIG. 15 illustrates a schematic circuit configuration of the powerdevice 8 using the power control circuit 2 according to embodiments ofthe present invention, which is a flyback LED illumination device. InFIG. 15, the illustration of diode bridge (DB) 14 is omitted. An inputvoltage V_(in) is corresponding to a full wave rectified waveform of therectified AC input.

As shown in FIG. 15, the power device 8 of the embodiments includes aninductor L_(P) connected to an AC wire side; a current sensing resistorR_(S) connected to ground potential; MOSFET Qs connected between theinductor L_(P) and the current sensing resistor R_(S) in series; and apower control circuit 2 coupled to the inductor L_(P), the MOSFET Qs andthe current sensing resistor R_(S) for performing QR control uponinductor-current I_(L) flowing through the inductor L_(P).

The power control circuit 2 includes a detection circuit 32 forperforming a detection of the inductor-current I_(L) flowing through theinductor L_(P); and a QR control circuit 30 connected to the detectioncircuit 32, the MOSFET Qs and the current sensing resistor R_(S),wherein when the inductor-current I_(L) of the inductor L_(P) isconducted in a discharging time sequence, the QR control circuit 30performs QR control upon the inductor-current I_(L) of the inductorL_(P) at a zero crossing point or a bottom point in the discharging timesequence based on an output of the detection circuit 32.

Herein, the detection circuit 32 may include an HPF connected to a drainof the MOSFET Qs connected to the inductor L_(P).

As shown in FIG. 15, the HPF includes a capacitor C_(F) connected to adrain of the MOSFET Qs; and a first resistor R_(f1) and a secondresistor R_(f2) connected between the capacitor C_(F) and the groundpotential in series; and a regulator terminal ZT of the QR controlcircuit 30 is connected to the connection point connecting the firstresistor R_(f1) and the second resistor R_(f2).

An output OUT is connected to a gate of the MOSFET Qs by the QR controlcircuit 30 for detecting current conducted in the HPF, and, when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, controlling the MOSFET Qs to be conductive ata zero point or a bottom point in the discharging time sequence based onan output of the detection circuit 32.

Further, the QR circuit 30 may be used for detecting current conductedin the current sensing resistor R_(S), and controlling the MOSFET Qs tobe non-conductive at a specific reset time point.

In the power device 8 according to embodiments of the present invention,as shown in FIG. 15, the inductor L_(P) is used as a primary winding ina flyback transformer 15. Further, a secondary winding Ls of the flybacktransformer 15 is connected to a diode rectifying circuit (D2-C2)including a diode D2 and a capacitor C2, and the capacitor C2 isconnected to a load (LED) in parallel. Furthermore, as shown in FIG. 15,the inductor L_(P) is connected to a buffer circuit (D3-R3-C3) includinga diode D3 in parallel, a resistor R3 and a capacitor C3. Othercomponents are similar to those in the power device 4 of embodiments ofthe present invention, and thus the associated descriptions are omitted.

By using the power device 8 according to embodiments of the presentinvention, the flyback LED illumination device includes an inductorL_(P) rather than an auxiliary winding inductor, so as to reduce thetotal weight and volume of the transformer, lower cost and increaseefficiency.

(QR DC/DC Converter)

FIG. 16 illustrates a schematic circuit configuration of the powerdevice 10 using the power control circuit 2 according to embodiments ofthe present invention, which is a QR type DC/DC converter.

In FIG. 16, an AC terminal is connected to a diode bridge (DB) 14 and aprimary winding L_(P) of a flyback transformer 15 via a filter circuit12.

As shown in FIG. 16, the power device 10 according to embodiments of thepresent invention includes an inductor L_(P) connected to an AC wireside; a current sensing resistor R_(S) connected to ground potential;MOSFET Qs connected between the inductor L_(P) and the current sensingresistor R_(S) in series; and a power control circuit 2 coupled to theinductor L_(P), the MOSFET Qs and the current sensing resistor R_(S) forperforming QR control to inductor-current I_(L) flowing through theinductor L_(P).

The power control circuit 2 includes a detection circuit 32 fordetecting the inductor-current I_(L) flowing through the inductor L_(P);and a QR control circuit 30 connected to the detection circuit 32, theMOSFET Qs and the current sensing resistor R_(S), wherein when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, the QR control circuit 30 performs QR controlupon the inductor-current I_(L) of the inductor L_(P) at a zero crossingpoint or a bottom point in the discharging time sequence based on anoutput of the detection circuit 32.

Herein, the detection circuit 32 may include an HPF connected to a drainof the MOSFET Qs connected to the inductor L_(P).

As shown in FIG. 16, the HPF includes a capacitor C_(F) connected to adrain of the MOSFET Qs; and a first resistor R_(f1) and a secondresistor R_(f2) connected between the capacitor C_(F) and the groundpotential in series; and a regulator terminal ZT of the QR controlcircuit 30 is connected to the connection point connecting the firstresistor R_(f1) and the second resistor R_(f2).

An output OUT is connected to a gate of the MOSFET Qs by the QR controlcircuit 30 for detecting current connected in the HPF, and, when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, controlling the MOSFET Qs to be conductive ata zero cross point or a bottom point in the discharging time sequencebased on an output of the detection circuit 32.

The QR control circuit 30 may be used for detecting current conducted inthe current sensing resistor R_(S), and controlling the MOSFET Qs to benon-conductive at a specific reset time point.

A secondary winding L_(s) of the flyback transformer 15 is connected toa diode rectifying circuit (D2-C2) including a diode D2 and a capacitorC2, and a DC output voltage V_(out) is obtained from an output of thecapacitor C2. Further, the DC output voltage V_(out) is fed back to afeedback terminal FB of the QR control circuit 30 at a primary side viaan error amplifier 18 and an insulation circuit (photoelectric coupler)20. As a result, a QR type DC/DC converter is formed by using the powerdevice 10 of the power control circuit 2 according to embodiments of thepresent invention. Other components are similar to those in the powerdevice 4, and thus the associated descriptions are omitted.

By using the power device 10 according to embodiments of the presentinvention, the QR type DC/DC converter includes an inductor L_(P) ratherthan an auxiliary winding inductor, so as to reduce the total weight andvolume of the transformer, lower cost and increase efficiency.

(AC/DC Converter)

FIG. 17 illustrates a schematic circuit configuration of the powerdevice 16 using the power control circuit 2 according to embodiments ofthe present invention, which is an AC/DC converter. Herein, as shown inFIG. 17, the AC/DC converter includes a power factor correction (PFC)circuit 60.

As shown in FIG. 17, an AC terminal is connected to the primary windingL_(P) of a flyback transformer 15 via a filter circuit 12, a diodebridge (DB) 14, a smoothing circuit (C_(D)-L_(D)), an anti-reflux diodeD_(D), and an electrolytic capacitor C_(E).

As shown in FIG. 17, the power device 16 of embodiments of the presentinvention includes an inductor L_(P) connected to an AC wire side; acurrent sensing resistor R_(S) connected to ground potential; MOSFET Qsconnected between the inductor L_(P) and the current sensing resistorR_(S) in series; and a power control circuit 2 coupled to the inductorL_(P), the MOSFET Qs and the current sensing resistor R_(S) forperforming QR control to inductor-current I_(L) flowing through theinductor L_(P).

The power control circuit 2 includes a detection circuit 32 fordetecting the inductor-current I_(L) flowing through the inductor L_(P);and a QR control circuit 30 connected to the detection circuit 32, theMOSFET Qs and the current sensing resistor R_(S), wherein when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, the QR control circuit 30 performs QR controlupon the inductor-current I_(L) of the inductor L_(P) at a zero crossingpoint or a bottom point in the discharging time sequence based on anoutput of the detection circuit 32.

Herein, the detection circuit 32 may include an HPF connected to a drainof the MOSFET Qs connected to the inductor L_(P).

As shown in FIG. 17, the HPF includes a capacitor C_(F) connected to adrain of the MOSFET Qs; and a first resistor R_(f1) and a secondresistor R_(f2) connected between the capacitor C_(F) and the groundpotential in series; and a regulator terminal ZT of a QR control circuit30 is connected to a connection point connecting the first resistorR_(f1) and the second resistor R_(f2).

An output OUT is connected to a gate of the MOSFET Qs by the QR controlcircuit 30 for detecting current conducted in the HPF, and, when theinductor-current I_(L) of the inductor L_(P) is conducted in adischarging time sequence, controlling the MOSFET Qs to be conductive ata zero cross point or a bottom point in the discharging time sequencebased on an output of the detection circuit 32.

The QR control circuit 30 may be used for detecting current conducted inthe current sensing resistor R_(S), and controlling the MOSFET Qs to benon-conductive at a specific reset time point.

A secondary winding L_(s) of the flyback transformer 15 is connected toa diode rectifying circuit (D2-C2) including a diode D2 and a capacitorC2, and a DC output voltage V_(out) is obtained from an output of thecapacitor C2. Further, the DC output voltage V_(out) is fed back to afeedback terminal FB of the QR control circuit 30 at a primary side viaan error amplifier 18 and an insulation circuit (photoelectric coupler)20.

Further, the PFC circuit 60 may be applied to control the on/off of theMOSFET Q_(PF) to control the connectivity between a connectionconnecting a primary side of the smoothing circuit (C_(D)-L_(D)) and theanti-reflux diode D_(D) and the ground potential. As a result, an AC/DCconverter capable of performing PFC and QR control is formed by using apower device 16 of the power control circuit 2 according to embodimentsof the present invention. In addition, the PFC circuit 60 and the QRcontrol circuit 30 may be implemented as an integrated PFC and QRcontrol circuit to form a single chip. Other components are similar tothose in the power device 4 of embodiments of the present invention, andthus the associated descriptions are omitted.

By using the power device 16 according to embodiments of the presentinvention, the AC/DC converter includes an inductor L_(P) for PFC and QRcontrol rather than an auxiliary winding inductor, so as to reduce thetotal weight and volume of the transformer, lower cost and increaseefficiency.

(Electronic Equipment)

The power control circuit 2 and the power device (4, 6, 8, 10, 16) usingthe power control circuit 2 may be installed in electronic equipment.For example, the electronic equipment may be applicable to a smartphone, a notebook PC (personal computer), a tablet computer, a monitoror TV, an external hard disk driver, a set top box, a vacuum, arefrigerator, a washing machine, a telephone, a facsimile machine, aprinter, a laser display, communication equipment, a server and etc.

In comparison with PWM control using a fixed frequency mode (PWM fixedfrequency control), the applications of the power control circuit 2 andthe power device (4, 6, 8, 10, 16) using the power control circuit 2according to embodiments of the present invention have the advantages oflow cost and high efficiency, such as an AC/DC converter an LEDillumination device, a DC/DC converter, and etc.

Further, the power control circuit 2 and the power device (4, 6, 8, 10,16) using the power control circuit 2 according to embodiments of thepresent invention are formed without an auxiliary winding, so as toreduce the total weight and volume of the transformer.

Hence, according to the present invention, a power control circuit, apower device and electronic equipment using the power control circuitare provided, in which quasi resonance is performed by using a coil inthe power control circuit, and current flowing in the coil is monitoredby a simple configuration for detecting a zero cross point or a bottomof a resonance.

OTHER EMBODIMENTS

Accordingly, the present invention is illustrated in the embodiments;however, the descriptions and drawings are exemplary illustrations andshould not be interpreted to limit the present invention. Personsskilled in the art should understand various substitute embodiments andtechnology according to the disclosure of the present invention.

Therefore, the present invention includes various embodiments which arenot described in this context.

APPLICABILITY IN INDUSTRY

The power control circuit and power device of the present invention areapplicable to an AC/DC converter, a DC/DC converter, an LED illuminationdevice, home appliance, mobile equipment and etc.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A power control circuit, comprising: a high passfilter, connected to a drain of a MOSFET, wherein the MOSFET is seriallyconnected between an inductor connected to an alternating-current wireand a current sensing resistor connected to a ground potential, and thehigh pass filter is arranged to generate a filtered output by blocking adirect current component of an inductor-current of the inductor; and aquasi resonance control circuit, connected to the high pass filter andthe MOSFET, wherein when the inductor-current of the inductor isconducted in a discharging time sequence, the quasi resonance controlcircuit performs quasi resonance control upon the inductor-current ofthe inductor at a zero crossing point or a bottom point in thedischarging time sequence based on the filtered output of the high passfilter inputted to the quasi resonance control circuit; wherein the highpass filter comprises: a capacitor, connected to the drain; and a firstresistor and a second resistor, connected between the capacitor and theground potential in series; and wherein the quasi resonance controlcircuit comprises: a current detection comparator, an inverting inputterminal of the current detection comparator is connected to aconnection point connecting the first resistor and the second resistor,and a reference voltage is input to an non-inverting input terminal ofthe current detection comparator; a Zener diode, connected between theinverting input terminal of the current detection comparator and aground terminal; an error amplifier, connected to the current sensingresistor; an RS trigger, a setting terminal of the RS trigger isconnected to an output of the current detection comparator and aresetting terminal of the RS trigger is connected to an output of theerror amplifier, and the RS trigger outputted a control signal of theMOSFET; and a buffer, connected to an output of the RS trigger, fordriving the MOSFET.
 2. The power control circuit of claim 1, wherein anoutput of the quasi resonance control circuit is connected to a gate ofthe MOSFET for detecting a current conducted in the high pass filter andfor controlling the MOSFET to be conductive at the zero cross point andthe bottom point.
 3. The power control circuit of claim 2, wherein thequasi resonance control circuit is used for detecting a currentconducted in the current sensing resistor, and for controlling theMOSFET to be non-conductive at a specific reset time point.
 4. The powercontrol circuit of claim 1, wherein the MOSFET is controlled to beconductive at a time point at which the RS trigger performs a settingaction, and the MOSFET is controlled to be non-conductive at a timepoint at which the RS trigger performs a resetting action.
 5. A powerdevice, comprising: an inductor, connected to an alternating-currentwire; a current sensing resistor, connected to a ground potential; aMOSFET, connected between the inductor and the current sensing resistorin series; a high pass filter, connected to a drain of the MOSFET,wherein the high pass filter is arranged to generate a filtered outputby blocking a direct current component of an inductor-current of theinductor; and a quasi resonance control circuit, connected to the highpass filter and the MOSFET, wherein when the inductor-current of theinductor is conducted in a discharging time sequence, the quasiresonance control circuit performs quasi resonance control upon theinductor-current of the inductor at a zero crossing point or a bottompoint in the discharging time sequence based on the filtered output ofthe high pass filter inputted to the quasi resonance control circuit;wherein the high pass filter comprises: a capacitor, connected to thedrain; and a first resistor and a second resistor, connected between thecapacitor and the ground potential in series; and wherein the quasiresonance control circuit comprises: a current detection comparator, aninverting input terminal of the current detection comparator isconnected to a connection point connecting the first resistor and thesecond resistor, and a reference voltage is input to an non-invertinginput terminal of the current detection comparator; a Zener diode,connected between the inverting input terminal of the current detectioncomparator and a ground terminal; an error amplifier, connected to thecurrent sensing resistor; an RS trigger, a setting terminal of the RStrigger is connected to an output of the current detection comparatorand a resetting terminal of the RS trigger is connected to an output ofthe error amplifier, and the RS trigger outputted a control signal ofthe MOSFET; and a buffer, connected to an output of the RS trigger, fordriving the MOSFET.
 6. The power device of claim 5, wherein an output ofthe quasi resonance control circuit is connected to a gate of the MOSFETfor detecting current conducted in the high pass filter, and forcontrolling the MOSFET to be conductive at the zero cross point and thebottom point.
 7. The power device of claim 6, wherein the quasiresonance control circuit is used for detecting a current conducted inthe current sensing resistor, and for controlling the MOSFET to benon-conductive at a specific reset time point.
 8. The power device ofclaim 5, wherein the MOSFET is controlled to be conductive at a timepoint at which the RS trigger performs a setting action, and the MOSFETis controlled to be non-conductive at a time point at which the RStrigger performs a resetting action.
 9. The power device of claim 5,wherein the power device is one of a buck LED illumination device, aboost LED illumination device and a flyback LED illumination device. 10.The power device of claim 5, wherein the power device is a quasiresonant DC/DC converter.
 11. The power device of claim 5, wherein thepower device is an AC/DC converter.
 12. The power device of claim 11,wherein the AC/DC converter comprises a power factor correction circuit.13. An electronic equipment, comprising the power device of claim
 5. 14.The electronic equipment of claim 13, wherein the electronic equipmentis one of a monitor, an external hard disk driver, a set top box, anotebook PC, a tablet PC, a smart phone, a battery charging system, apersonal calculator, a display, a printer, a vacuum, a refrigerator, afacsimile machine, a telephone, communication equipment and a server.15. A power control circuit, comprising: a high pass filter, connectedto a drain of a MOSFET, wherein the MOSFET is serially connected betweenan inductor connected to an alternating-current wire and a currentsensing resistor connected to a ground potential, and the high passfilter is arranged to generate a filtered output by blocking a directcurrent component of an inductor-current of the inductor; and a quasiresonance control circuit, connected to the high pass filter and theMOSFET, wherein when the inductor-current of the inductor is conductedin a discharging time sequence, the quasi resonance control circuitperforms quasi resonance control upon the inductor-current of theinductor at a zero crossing point or a bottom point in the dischargingtime sequence based on the filtered output of the high pass filterinputted to the quasi resonance control circuit, wherein the zerocrossing point or the bottom point is determined by the output of thehigh pass filter; wherein the high pass filter comprises: a capacitor,connected to the drain; and a first resistor and a second resistor,connected between the capacitor and the ground potential in series; andwherein the quasi resonance control circuit comprises: a currentdetection comparator, an inverting input terminal of the currentdetection comparator is connected to a connection point connecting thefirst resistor and the second resistor, and a reference voltage is inputto an non-inverting input terminal of the current detection comparator;a Zener diode, connected between the inverting input terminal of thecurrent detection comparator and a ground terminal; an error amplifier,connected to the current sensing resistor; an RS trigger, a settingterminal of the RS trigger is connected to an output of the currentdetection comparator and a resetting terminal of the RS trigger isconnected to an output of the error amplifier, and the RS triggeroutputted a control signal of the MOSFET; and a buffer, connected to anoutput of the RS trigger, for driving the MOSFET.
 16. The power controlcircuit of claim 15, wherein an output of the quasi resonance controlcircuit is connected to a gate of the MOSFET for detecting a currentconducted in the high pass filter and for controlling the MOSFET to beconductive at the zero cross point and the bottom point.
 17. The powercontrol circuit of claim 16, wherein the quasi resonance control circuitis used for detecting a current conducted in the current sensingresistor, and for controlling the MOSFET to be non-conductive at aspecific reset time point.
 18. The power control circuit of claim 15,wherein the MOSFET is controlled to be conductive at a time point atwhich the RS trigger performs a setting action, and the MOSFET iscontrolled to be non-conductive at a time point at which the RS triggerperforms a resetting action.
 19. A power control circuit, comprising: ahigh pass filter, connected to a drain of a MOSFET, wherein the MOSFETis serially connected between an inductor connected to analternating-current wire and a current sensing resistor connected to aground potential; and a quasi resonance control circuit, connected tothe high pass filter and the MOSFET, wherein when an inductor-current ofthe inductor is conducted in a discharging time sequence, the quasiresonance control circuit performs quasi resonance control upon theinductor-current of the inductor at a zero crossing point or a bottompoint in the discharging time sequence based on an output of the highpass filter, wherein the high pass filter comprises: a capacitor,connected to the drain; and a first resistor and a second resistor,connected between the capacitor and the ground potential in series; andwherein the quasi resonance control circuit comprises: a currentdetection comparator, an inverting input terminal of the currentdetection comparator is connected to a connection point connecting thefirst resistor and the second resistor, and an reference voltage isinput to an non-inverting input terminal of the current detectioncomparator; a Zener diode, connected between the inverting inputterminal of the current detection comparator and a ground terminal; anerror amplifier, connected to the current sensing resistor; an RStrigger, a setting terminal of the RS trigger is connected to an outputof the current detection comparator and a resetting terminal of the RStrigger is connected to an output of the error amplifier, and the RStrigger outputted a control signal of the MOSFET; and a buffer,connected to an output of the RS trigger, for driving the MOSFET. 20.The power control circuit of claim 19, wherein an output of the quasiresonance control circuit is connected to a gate of the MOSFET fordetecting a current conducted in the high pass filter and forcontrolling the MOSFET to be conductive at the zero cross point and thebottom point.
 21. The power control circuit of claim 20, wherein thequasi resonance control circuit is used for detecting a currentconducted in the current sensing resistor, and for controlling theMOSFET to be non-conductive at a specific reset time point.
 22. Thepower control circuit of claim 19, wherein the MOSFET is controlled tobe conductive at a time point at which the RS trigger performs a settingaction, and the MOSFET is controlled to be non-conductive at a timepoint at which the RS trigger performs a resetting action.
 23. The powercontrol circuit of claim 19, wherein in the high pass filter, a directcurrent component of an high pass filter terminal voltage at aconnection point connecting the capacitor and the first resistor isblocked by the capacitor, and a potential difference between a highlevel and a low level is the same level as a potential difference of adrain voltage of the MOSFET, and in the quasi resonance control circuit,in comparison with the drain voltage of the MOSFET, a regulator terminalvoltage at the connection point connecting the first resistor and thesecond resistor of the regulator terminal connected to the quasiresonance control circuit is reduced and becomes as a differentialwaveform with a peak shape.
 24. A power device, comprising: aregeneration capacitor, connected to an alternating-current wire; aninductor, one end of the inductor connected to the regenerationcapacitor; a diode, connected between another end of the inductor andthe alternating current wire; a load, connected to the regenerationcapacitor in parallel; a current sensing resistor, connected to a groundpotential; a MOSFET, connected between another end of the inductor andthe current sensing resistor in series; a high pass filter, connected toa drain of the MOSFET; and a quasi resonance control circuit, connectedto the high pass filter and the MOSFET, wherein when an inductor-currentof the inductor is conducted in a discharging time sequence, the quasiresonance control circuit performs quasi resonance control upon theinductor-current of the inductor at a zero crossing point or a bottompoint in the discharging time sequence based on an output of the highpass filter, wherein the high pass filter comprises: a capacitor,connected to the drain; and a first resistor and a second resistor,connected between the capacitor and the ground potential in series; andwherein the quasi resonance control circuit comprises: a currentdetection comparator, an inverting input terminal of the currentdetection comparator is connected to a connection point connecting thefirst resistor and the second resistor, and an reference voltage isinput to an non-inverting input terminal of the current detectioncomparator; a Zener diode, connected between the inverting inputterminal of the current detection comparator and a ground terminal; anerror amplifier, connected to the current sensing resistor; an RStrigger, a setting terminal of the RS trigger is connected to an outputof the current detection comparator and a resetting terminal of the RStrigger is connected to an output of the error amplifier, and the RStrigger outputted a control signal of the MOSFET; and a buffer,connected to an output of the RS trigger, for driving the MOSFET. 25.The power device of claim 24, wherein an output of the quasi resonancecontrol circuit is connected to a gate of the MOSFET for detectingcurrent conducted in the high pass filter, and for controlling theMOSFET to be conductive at the zero cross point and the bottom point.26. The power device of claim 25, wherein the quasi resonance controlcircuit is used for detecting a current conducted in the current sensingresistor, and for controlling the MOSFET to be non-conductive at aspecific reset time point.
 27. The power device of claim 24, wherein theMOSFET is controlled to be conductive at a time point at which the RStrigger performs a setting action, and the MOSFET is controlled to benon-conductive at a time point at which the RS trigger performs aresetting action.
 28. The power device of claim 24, wherein the powerdevice is a buck LED illumination device or a boost LED illuminationdevice.
 29. The power device of claim 24, wherein in the high passfilter, a direct current component of an high pass filter terminalvoltage at a connection point connecting the capacitor and the firstresistor is blocked by the capacitor, and a potential difference betweena high level and a low level is the same level as a potential differenceof a drain voltage of the MOSFET, and in the quasi resonance controlcircuit, in comparison with the drain voltage of the MOSFET, a regulatorterminal voltage at the connection point connecting the first resistorand the second resistor of the regulator terminal connected to the quasiresonance control circuit is reduced and becomes as a differentialwaveform with a peak shape.
 30. An electronic equipment, comprising thepower device of claim
 24. 31. The electronic equipment of claim 30,wherein the electronic equipment is one of a monitor, an external harddisk driver, a set top box, a notebook PC, a tablet PC, a smart phone, abattery charging system, a personal calculator, a display, a printer, avacuum, a refrigerator, a facsimile machine, a telephone, communicationequipment and a server.
 32. A power device, comprising: a load,connected to an alternating-current wire; an inductor, connected to theload in series; a current sensing resistor, connected to a groundpotential; a MOSFET, connected between the inductor and the currentsensing resistor in series; a high pass filter, connected to a drain ofthe MOSFET; and a quasi resonance control circuit, connected to the highpass filter and the MOSFET, wherein when an inductor-current of theinductor is conducted in a discharging time sequence, the quasiresonance control circuit performs quasi resonance control upon theinductor-current of the inductor at a zero crossing point or a bottompoint in the discharging time sequence based on an output of the highpass filter, wherein the high pass filter comprises: a capacitor,connected to the drain; and a first resistor and a second resistor,connected between the capacitor and the ground potential in series; andwherein the quasi resonance control circuit comprises: a currentdetection comparator, an inverting input terminal of the currentdetection comparator is connected to a connection point connecting thefirst resistor and the second resistor, and an reference voltage isinput to an non-inverting input terminal of the current detectioncomparator; a Zener diode, connected between the inverting inputterminal of the current detection comparator and a ground terminal; anerror amplifier, connected to the current sensing resistor; an RStrigger, a setting terminal of the RS trigger is connected to an outputof the current detection comparator and a resetting terminal of the RStrigger is connected to an output of the error amplifier, and the RStrigger outputted a control signal of the MOSFET; and a buffer,connected to an output of the RS trigger, for driving the MOSFET. 33.The power device of claim 32, wherein in the high pass filter, a directcurrent component of an high pass filter terminal voltage at aconnection point connecting the capacitor and the first resistor isblocked by the capacitor, and a potential difference between a highlevel and a low level is the same level as a potential difference of adrain voltage of the MOSFET, and in the quasi resonance control circuit,in comparison with the drain voltage of the MOSFET, a regulator terminalvoltage at the connection point connecting the first resistor and thesecond resistor of the regulator terminal connected to the quasiresonance control circuit is reduced and becomes as a differentialwaveform with a peak shape.
 34. A power control circuit, comprising: ahigh pass filter, connected to a drain of a MOSFET, wherein the MOSFETis serially connected between an inductor connected to analternating-current wire and a current sensing resistor connected to aground potential, and the high pass filter is arranged to generate anoutput by blocking a direct current component of an inductor-current ofthe inductor; and a quasi resonance control circuit, connected to thehigh pass filter and the MOSFET, wherein when the inductor-current ofthe inductor is conducted in a discharging time sequence, the quasiresonance control circuit performs quasi resonance control upon theinductor-current of the inductor at a zero crossing point or a bottompoint in the discharging time sequence based on the output of the highpass filter; wherein the high pass filter comprises: a capacitor,connected to the drain; and a first resistor and a second resistor,connected between the capacitor and the ground potential in series; andwherein the quasi resonance control circuit comprises: a currentdetection comparator, an inverting input terminal of the currentdetection comparator is connected to a connection point connecting thefirst resistor and the second resistor, and an reference voltage isinput to an non-inverting input terminal of the current detectioncomparator; a Zener diode, connected between the inverting inputterminal of the current detection comparator and a ground terminal; anerror amplifier, connected to the current sensing resistor; an RStrigger, a setting terminal of the RS trigger is connected to an outputof the current detection comparator and a resetting terminal of the RStrigger is connected to an output of the error amplifier, and the RStrigger outputted a control signal of the MOSFET; and a buffer,connected to an output of the RS trigger, for driving the MOSFET.
 35. Apower device, comprising: an inductor, connected to analternating-current wire; a current sensing resistor, connected to aground potential; a MOSFET, connected between the inductor and thecurrent sensing resistor in series; a high pass filter, connected to adrain of the MOSFET, wherein the high pass filter is arranged togenerate an output by blocking a direct current component of aninductor-current of the inductor; and a quasi resonance control circuit,connected to the high pass filter and the MOSFET, wherein when theinductor-current of the inductor is conducted in a discharging timesequence, the quasi resonance control circuit performs quasi resonancecontrol upon the inductor-current of the inductor at a zero crossingpoint or a bottom point in the discharging time sequence based on thefiltered output of the high pass filter inputted to the quasi resonancecontrol circuit; wherein the high pass filter comprises: a capacitor,connected to the drain; and a first resistor and a second resistor,connected between the capacitor and the ground potential in series; andwherein the quasi resonance control circuit comprises: a currentdetection comparator, an inverting input terminal of the currentdetection comparator is connected to a connection point connecting thefirst resistor and the second resistor, and an reference voltage isinput to an non-inverting input terminal of the current detectioncomparator; a Zener diode, connected between the inverting inputterminal of the current detection comparator and a ground terminal; anerror amplifier, connected to the current sensing resistor; an RStrigger, a setting terminal of the RS trigger is connected to an outputof the current detection comparator and a resetting terminal of the RStrigger is connected to an output of the error amplifier, and the RStrigger outputted a control signal of the MOSFET; and a buffer,connected to an output of the RS trigger, for driving the MOSFET.
 36. Apower control circuit, comprising: a high pass filter, connected to adrain of a MOSFET, wherein the MOSFET is serially connected between aninductor connected to an alternating-current wire and a current sensingresistor connected to a ground potential, and the high pass filter isarranged to generate an output by blocking a direct current component ofan inductor-current of the inductor; and a quasi resonance controlcircuit, connected to the high pass filter and the MOSFET, wherein whenthe inductor-current of the inductor is conducted in a discharging timesequence, the quasi resonance control circuit performs quasi resonancecontrol upon the inductor-current of the inductor at a zero crossingpoint or a bottom point in the discharging time sequence based on thefiltered output of the high pass filter inputted to the quasi resonancecontrol circuit, wherein the zero crossing point or the bottom point isdetermined by the output of the high pass filter; wherein the high passfilter comprises: a capacitor, connected to the drain; and a firstresistor and a second resistor, connected between the capacitor and theground potential in series; and wherein the quasi resonance controlcircuit comprises: a current detection comparator, an inverting inputterminal of the current detection comparator is connected to aconnection point connecting the first resistor and the second resistor,and an reference voltage is input to an non-inverting input terminal ofthe current detection comparator; a Zener diode, connected between theinverting input terminal of the current detection comparator and aground terminal; an error amplifier, connected to the current sensingresistor; an RS trigger, a setting terminal of the RS trigger isconnected to an output of the current detection comparator and aresetting terminal of the RS trigger is connected to an output of theerror amplifier, and the RS trigger outputted a control signal of theMOSFET; and a buffer, connected to an output of the RS trigger, fordriving the MOSFET.